Light-sensitive photographic element



Aug. 18, 1953 H. DAVIS 2,649,375

LIGHT-SENSITIVE PHOTOGRAPHIC ELEMENT Filed Oct. 26, 1950 v PHOTOGRAPH/C A/wen HAL/DE EMULSION CELLULOJE EJTER CONTAIN/N6 LESS THAN 0.002% 7-D/fTHYLAMlN0-4-METHYLCOUMARIN H4RRY I. DAVIS I N VEN TOR ATTORNEY C'f AGENT Patented Aug. 18, 1953 LIGHT-SENSITIVE PHOTOGRAPHIC ELEMENT Harry I. Davis, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application October 26, 1950, Serial No. 192,285

10 Claims. (01. 95-9) This invention relates to photographic elements and a method for identifying them.

Motion picture film is ordinarily identified according to the manufacturer and type (c. g. cellu-" lose acetate or cellulose nitrate) by exposing letters or symbols photographically along the margins of the raw or unprocessed film. Upon development, these markings become visible and permit identification of the film.

The diificulty with such a means of identification is that each foot of film must be separately inspected, which is a somewhat laborious process. Identification is made even more difiicult when separate lots of film are spliced together and difierent types of film are made into a single strip. Rapid identification of film is quite important in recovery of scrap film or in the vault storage of film, where cellulose acetate type must be distinguished from cellulose nitrate type film.

It is, therefore, an object of my invention to port containing from 0.0001 to 0.002 per cent by weight, based on the cellulose ester, of 7-diethylamino-4-methylcoumarin. On inspection of the photographic element under ultra-violet radiation, a purplish fluorescence of sufiicient intensity for identification purposes is exhibited.

It is known that fluorescent materials can be added to the film base of photographic elements. For example, Michaelis U. S. Patent 2,331,492, dated October 12 1943, describes a photographic element containing a fluorescent material, such as rhodamine, in the film base. The purpose of the fluorescent layer of Michaelis is to provide a source of radiant energy to cause exposure of a light-sensitive emulsion, which is not sensitive to primary radiation. Other patents show the use of fluorescent materials in the film base of a photographic element for the purpose of image intensification. I have now found that by using very small amounts of 7-diethylamino- 4-methlycoumarin in the film base of a photographic element, the fluorescent properties of the 7-diethylamino-4-methylcoumarin have no substantial effect on the light-sensitive emulsion layer, but are sufiicient to permit identification of the photographic element upon inspection un- Other objects will beder ultra-violet radiation. It was most unexpected to find that over a certain range 7-diethylamino-4-methylcoumarin could be advantageously used without having a deleterious effect on the photographic emulsion. 7-diethylamino- 4-methylcoumarin has no detectable effect on the color of the film base and is insoluble in water or the solutions used in film processing, when used in accordance with the process of my invention.

Whereas the use of fluorescent materials in inks and the like for identifying certain materials has long been known, many of these materials are unsuited for use in connection with the identification of photographic elements because of their adverse efiect on the color of the film base or their fogging action on the light-sensitive emulsion coated on the base. These and other difiiculties are avoided when 7-diethylamino-4- methylcoumarin is used as the fluorescent material in photographic elements in accordance with my invention.

In the copending application Serial No. 191,017, filed on October 19, 1950, of Ralph H. Talbot, a method for identifying photographic elements comprising adding small amounts of anthracene to the film base, e. g. cellulose acetate, is described. While the method of that application offers certain advantages over the prior art, I have found that the 7-diethylamino-4-methylcoumarin of my invention offers further advantages in that the coumarin compoundis effective in amounts varying from about one-fortieth to one-fiftieth of the anthracene.

'7-diethylamino-4-methylcoumarin is a known substance and has been described in Miglarese U. S. Patent 2,334,348, dated November 16, 1943. Its structure can be represented as follows:

The accompanying drawing shows a film base of a cellulose ester containing 7-diethylamino-4- methylcoumarin and a coating of a photographic silver halide emulsion on the film base. A further description of the photographic elements of my invention is given below.

The amount of 7-diethylamino-4-methylcoumarin used in my invention is of material importance in determining the properties of the cellulose ester film base, and consequently, the photographic element comprising the cellulose ester film base. An amount less than 0.0001 per cent should not be used, nor should an amount in excess of 0.002 per cent be used, the amounts being based on the cellulose ester, since the advantageous results of my invention are not obtained outside this range.

The 7 diethylamino-4-methylcoumarin can advantageously be added to a viscous solution or dope of the cellulose ester, and the composition agitated until homogeneity is accomplished. The 7-diethylamino-4-methylcoumarin can be. added in solid form, or in the form of a solution, which contains, for example, the same solvent present in the cellulose ester dope. After intimate mixing the solution is cast into a sheet and the solvent removed by evaporation. A film of the cellulose ester can be first formed, and a coating of '7-diethylamino-4-methylcoumarin applied to the cellulose ester layer, although I have found that a product is obtained which does not exhibit the homogeneity and. abrasion resistance shown by the product obtained from a cellulose ester dope containing the '7-diethylamino-4- methylcoumarin. A film of cellulose ester can also be immersed in a solution of the I-diethylaminoi-methylcoumarm in a solvent having no dissolving power for the cellulose ester. Such modes of procedure are not generally to be preferred since. the amount. of 7-diethylamino-4- methylcoumarin used cannot be as systematic-ally controlled and the 7-diethylamino-a-methylcoumarin is easily removed from the film base during handling.

Cellulose esters which can advantageously be used in my invention comprise cellulose acetate, cellulose propionate, cellulose butyrate, etc., mixed cellulose esters, such as cellulose acetate butyrate, etc. My invention is particularly adaptable to the use of cellulose acetate containing, for example, from 35 to 44.8 per cent acetyl. The particular solvent, or mixture of solvents, used in the cellulose ester dope will depend on the acyl content of the ester. For example, cellulose acetate containing from about 39 to 41 per cent acetyl can be dissolved in acetone.

Cellulose acetate containing from about 42.5 to 44.0 per cent acetyl has been found to be especially useful in preparing the photographic elements of my invention. A range of acetyl from 43.0 to 43.5 per cent gives particularly useful results. The 7-diethylamino-4methy1cournarin can readily be incorporated into such esters by addition to a solution of the ester in a solvent mixture composed of 55 to 85 per cent by weight of methylene chloride, 15 to per cent by weight of methanol or ethanol, and 30 to 5 per cent by weight of ethylene chloride. By replacing the ethylene chloride with propylene chloride, the methylene chloride can comprise from 65 to 90 per cent by Weight of the solvent mixture. Cellulose acetate containing from 42.5 to 44.0 per cent by weight, and more particularly from 43.0 to 43.5 per cent by weight, of acetyl provides a film base possessing unusual resistance to tear and separation when subjected to stress or strain. (-See, for example, Fordyce et a1. U. S. Patents 2,492,977 and 2,492,978, dated January 3 19 50.)

The accompanying drawing illustrates, schematically, a cross sectional view of a photographic element representative of those of my invention. The element comprises a support [0 of a cellulose ester, e. g. cellulose acetate of 43 per cent acetyl content containing less than 0.002 per cent (e. g. 0.0004 per cent) of 7-diethylamino-4-methylcoumarin and having thereon. a

4 photographic silver-halide emulsion ll. Instead of a single photographic silver-halide emulsion, the support 10 can be coated with a plurality of emulsions, for example, as shown in U. S. Patents 2,350,764, dated June 6, 1944; 2,360,214, dated October 10, 1944; 2,376,202, dated May 15, 1945; 2,391,198, dated December 18, 1945; 2,403,721, dated July 9, 1946; etc. The photographic emulsion layer II, and those described in the above U1. S. patents are the usual gelatino-silver halide emulsions customarily used in the art of blackand-white or multi-color reproduction. These emulsions can also consist of silver halide dispersed in other water-permeable colloidal materials, such as synthetic resins, e. g. polyvinyl alcohol, etc., cellulose ethers and esters, etc. Typical silver-halide emulsions include silver chloride, bromide, bromiodide, and chlorobromide types. The photographic silver-halide emulsions can contain the usual addenda, such as polymethine sensitizing dyes, anti-foggants, etc.

What I claim as my invention and desire secured by Letters Patent of the United States 1. A photographic element comprising at least one photographicvsilver halide emulsion layer and a colorless cellulose ester layer containing from 0.0001 to 0.002 per cent by weight, based on the cellulose ester, of 7-diethylamino-4-methylcoumarin, said cellulose ester being an ester of a saturated carboxylic acid containing from. 2 to 4 carbon atoms.

2. A photographic element comprising at least one photographic silver halide emulsion layer and a colorless cellulose acetate layer containing from 0.0001 to 0.002 per cent by weight, based on the cellulose acetate, of 7-diethylamino-4- methylcoumarin.

3. A. photographic clement comprising at least one photographic silver bromide emulsion layer and a colorless cellulose ester layer containing from 0.0001 to 0.002 per centby weight, based on the cellulose ester, of 7-diethylamino-4-methylcoumarin, said cellulose ester being an ester of a saturated carboxylic acid containing from 2 to 4 carbon atoms.

4. A. photographic element comprising at leastone photographic silver chloride emulsion layer and a colorless cellulose ester layer containing from 0.0001 to 0.002 per cent by Weight, based on the cellulose ester, or 7-diethylamino-4methylcoumarin, said cellulose ester being an ester of a saturated carboxylic acid containing from 2 to 4 carbon atoms.

5. A photographic element comprising at least one photographic silver bromiodide emulsion layer and a colorless cellulose ester layer containing from 0.0001 to 0.002 er cent by weight, based on the cellulose ester, of 7-diethylamino-4- methylcoumarin, said cellulose ester being an ester of a saturatedcarboxylic acid containing from 2 to 4 carbon atoms.

6. A photographic element comprising at least one photographic silver chlorobromide emulsion layer and a colorless cellulose ester layer containing from 0.0001 to 0.002 per cent by weight, based on the cellulose ester, of 7-diethylamino- 4-methylcoumarin, said cellulose ester being an ester of a saturated carboxylic acid containing from 2 to 4 carbon atoms.

'7. A photographic element comprising at least one photographic silver bromide emulsion layer and a colorless. cellulose acetate layer containing from 0.00.01 to 0.002 per cent by weight, based on the cellulose acetate, of 7-diethylamino-4- methylcoumarin.

8. A photographic element comprising at least one photographic silver chloride emulsion layer and a colorless cellulose acetate layer containing from 0.0001 to 0.002 per cent by Weight, based on the cellulose acetate, of 7-diethylamino-4- inethylcoumarin.

9. A photographic element comprising at least one photographic silver bromiodide emulsion layer and a colorless cellulose acetate layer containing from 0.0001 to 0.002 per cent by Weight, based on the cellulose acetate, of '7-diethylamino- 4-niethylcoumarin.

10. A photographic element comprising at 1 least one photographic silver chlorobromide emulsion layer and a colorless cellulose acetate layer containing from 0.0001 to 0.002 per cent by Weight, based on the cellulose acetate, of 7-cliethylamino-4methylcoumarin.

HARRY I. DAVIS.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A PHOTOGRAPHIC ELEMENT COMPRISING AT LEAST ONE PHOTOGRAPHIC SILVER HALIDE EMULSION LAYER AND A COLORLESS CELLULOSE ESTER LAYER CONTAINING FROM 0.0001 TO 0.0002 PER CENT BY WEIGHT, BASED ON THE CELLULOSE ESTER, OF 7-DIETHYLAMINO-4-METHYLCOUMARIN, SAID CELLULOSE ESTER BEING AN ESTER OF A SATURATED CARBOXYLIC ACID CONTAINING FROM 2 TO 4 CARBON ATOMS. 